[Everyday C#] PR 13: Expressions and Statements

[BillWagner]

Fixes #53555

Create a new fundamentals/statements/ section with two concept articles (selection statements, iteration statements), each with its own snippet project, and register a new Expressions and statements TOC group. All content is net-new, so no redirects are needed. Follows the Strings section conventions (PRs 10–12).

---

Internal previews

📄 File	🔗 Preview link
docs/csharp/fundamentals/statements/iteration-statements.md	Iteration statements
docs/csharp/fundamentals/statements/selection-statements.md	"Selection statements in C#"
docs/csharp/toc.yml	Taken from https://github.com/dotnet/roslyn/wiki/Samples-and-Walkthroughs

[Copilot]

Pull request overview

Adds a new Expressions and statements group to the C# Fundamentals docs, introducing two new concept articles (selection statements and iteration statements) with dedicated snippet projects that match the existing Fundamentals/Strings snippet structure.

Changes:

• Registered a new Expressions and statements group in docs/csharp/toc.yml with links to two new articles.
• Added new concept articles for selection statements and iteration statements under docs/csharp/fundamentals/statements/.
• Added new, buildable snippet projects for both articles under docs/csharp/fundamentals/statements/snippets/.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/csharp/toc.yml	Adds the new TOC group and links to the two new Fundamentals articles.
docs/csharp/fundamentals/statements/selection-statements.md	New concept article that references selection-statement snippets via :::code.
docs/csharp/fundamentals/statements/iteration-statements.md	New concept article that references iteration-statement snippets via :::code.
docs/csharp/fundamentals/statements/snippets/selection-statements/selection-statements.csproj	New snippet project targeting net10.0, consistent with existing Fundamentals snippet projects.
docs/csharp/fundamentals/statements/snippets/selection-statements/Program.cs	New selection statement examples with snippet region markers used by the article.
docs/csharp/fundamentals/statements/snippets/iteration-statements/iteration-statements.csproj	New snippet project targeting net10.0, consistent with existing Fundamentals snippet projects.
docs/csharp/fundamentals/statements/snippets/iteration-statements/Program.cs	New iteration statement examples (including await foreach) with snippet region markers used by the article.